Hybrid imaging apparatus and methods for interactive procedures

ABSTRACT

An imaging system includes an x-ray assembly having one or more x-ray sources configured to be energized at multiple positions. A control program energizes the one or more x-ray sources in a programmed sequence and controls the timing of the sequence.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.62/127,387, filed Mar. 3, 2015, in the name of Wang et al., and entitledHYBRID IMAGING METHODS FOR INTERACTIVE PROCEDURES.

This application is related in certain respects to U.S. patentapplication Ser. No. 14/190,447, filed Feb. 26, 2014, in the name ofWang et al., and entitled IMAGING SYSTEM AND METHOD FOR PORTABLESTEREOSCOPIC TOMOGRAPHY, which is incorporated herein by reference inits entirety.

TECHNICAL FIELD

The disclosure relates generally to the field of radiography and moreparticularly to apparatus and methods for adaptively generating anddisplaying images of different types to track progress of a procedure inmultiple modalities from the same radiography system.

BACKGROUND

A wide range of invasive and exploratory medical procedures areperformed with the aid of fluoroscopic imaging equipment for monitoringprogress. Fluoroscopy provides “real-time” radiographic imaging that maybe particularly useful for tracking motion that is related to adiagnostic procedure and is often used to monitor progress of aniodinated contrast agent or to help a practitioner in guiding a catheterthrough the veins of a patient in order to reach a location in thepatient's body that requires some form of treatment, e.g., the site of atumor or abscess.

The fluoroscopy-guided process of catheter placement and guidancerequires considerable skill and often entails an amount of risk.Guidance procedures may be time consuming and may be difficult toexecute, since the ability to visualize a catheter tip as itprogressively advances through complex venous structures is inhibited byproblems such as poor subject contrast, obstructed visibility, and doseconstraints. Once a catheter is appropriately positioned, a treatmentdelivery device may be inserted through the catheter to the site of theabnormality and a treatment applied. For example, the treatment mayinvolve embolization to cut off the blood supply that feeds a tumor, orto ablate a tumor using thermal methods, or, in the case of an abscess,to drain infectious material.

Conventionally, radiographic imaging to support state-of-the-artinterventional procedures uses expensive, specialized C-arm systems thatposition the x-ray source and detector in fixed position with respect toeach other and allow a limited level of flexibility in placement of thesource-detector pair about the object that is to be imaged. C-armfluoroscopy systems are equipped with high frame rate flat paneldetectors that provide two-dimensional (2-D) images. Supportingcomponents for these imaging systems may include heads-up monitors, forexample, that allow the practitioner to view the progress of aninterventional procedure, such as catheter insertion or a surgicaloperation.

One limitation of conventional imaging systems used for fluoroscopyrelates to the need for repositioning of C-arm components at variouspoints during a procedure. Visibility of a catheter device or ofcontrast agent progress may be obscured at particular angles orpositions so that adjustment of source and detector positioning isrequired in order to maintain useful tracking. In some cases, the neededmovement of the C arm may interfere with the procedure or require thatthe practitioner shift position to allow C arm movement, which can beundesirable.

Another limitation of conventional imaging systems used for fluoroscopyrelates to the lack of depth information. Systems dedicated solely tofluoroscopic imaging are optimized to show movement in real-time, butprovide only 2-dimensional (2-D) images to the viewer. A separatetomography or other depth imaging apparatus must be used if depthinformation is to be obtained.

Tomography (also referred to as x-ray computed tomography or computedtomography (CT)) is a well known medical imaging method that usescomputer processing to acquire and combine image data from multipleangles. In computed tomography, digital image processing is used togenerate a three-dimensional image of the inside of an object from aseries/collection of two-dimensional x-ray images taken around a singleaxis of rotation. In an idealized CT apparatus, a source/detector makesone or more complete 360-degree rotations about the subject obtaining acomplete volume of data from which images may be reconstructed. Thevolume of data produced by the CT system is manipulated to generatedepth images of various internal structures. The images may be generatedin the axial or transverse plane (e.g., perpendicular to the long axisof the body), or reformatted in various planes, or volumetricthree-dimensional representations.

Tomosynthesis combines digital image capture and processing with someportion of the source/detector motion used in tomography. While thereare some similarities to CT, tomosynthesis has a number of differencesfrom CT as conventionally practiced and is largely considered as aseparate technique. As noted above, in CT, the source/detector makes acomplete 360-degree rotation about the subject obtaining a complete setof data from which images may be reconstructed. By contrast, digitaltomosynthesis uses a small rotation angle (e.g., 30 degrees) with asmall number of discrete slices/exposures (e.g., 25-70 exposures). Thisset of data, incomplete with regard to full volume image information, isdigitally processed to yield images similar to tomography but with abroader depth of field. Since the image is digitally generated andrepresented, various processing techniques may be used to generate andpresent a series of slices at different tissue depths and with differentthicknesses reconstructed from the same image acquisition, therebysaving time and reducing radiation exposure.

Acquired tomosynthesis data may be incomplete in terms of the full threedimensions of data content. Tomosynthesis offers higher depth resolutionin image slices parallel to a detector than CT offers, while CT mayprovide better isotropic resolution. Tomosynthesis is advantaged over2-D radiography as it provides a measure of depth detail that is nototherwise available with conventional radiography. Moreover, the limiteddepth detail information that it offers can be of value to supplementfluoroscopic display. The resulting depth display provides improvedvisualization over conventional 2-D image presentation and, even thoughit may not be available in real-time as is 2-D fluoroscopy,tomosynthesis imaging, if performed at near real-time speeds, could beparticularly helpful for guiding interventional procedures.

Thus, it can be seen that there is a need for a portable imagingapparatus that is capable of providing fluoroscopic imaging as well asdepth imaging such as tomosynthesis imaging to help track progress forclinical and interventional procedures. There would be particular valuein imaging apparatus and techniques that allow an imaging apparatus toswitch rapidly between depth imaging and fluoroscopy at suitable angles,without requiring corresponding repositioning of the x-ray sources anddetector.

SUMMARY

An object of the present disclosure is to address the need for imagingapparatus to support tracking of medical procedures internal to apatient. Tracking may be provided by 2-D fluoroscopic imaging incombination with tomosynthesis imaging for providing some measure ofdepth information. A related object of the present disclosure is toprovide these different imaging functions from a single imagingapparatus that operates in different modes and easily switches betweenimage acquisition modes, and display modes.

These objects are given only by way of illustrative example, and suchobjects may be exemplary of one or more embodiments of the invention.Other desirable objectives and advantages inherently achieved by thedisclosed apparatus may occur or become apparent to those skilled in theart. The invention is defined by the appended claims.

In one embodiment, an x-ray assembly is configured to be energizable toemit ionizing radiation from one or multiple different spatial positionstoward an imaging region of a patient. Control hardware energizes thex-ray assembly at predetermined times at one or more of the spatialpositions. One mode of operation allows energizing the x-ray assemblyone or more times from a first spatial position toward the imagingregion of the patient, while a second mode of operation allowsenergizing the x-ray assembly multiple times each from a different oneof the spatial positions. The control hardware is configured to switchan operating mode of the imaging system between the first and secondmodes during one medical image examination, or medical process occurringin the imaging region of the patient.

In another embodiment, a method of operating an imaging system includesproviding a plurality of x-ray sources, energizing one of the x-raysources multiple times at one predetermined position and capturing afirst plurality of radiographic images of a subject thereby. The one ormore x-ray sources are energized multiple times at differentpredetermined positions and a second plurality of radiographic images ofthe subject are captured thereby corresponding to the differentpredetermined positions. At least a portion of the captured images areused in reconstructing a tomosynthesis image. Furthermore, the step ofcapturing can be repeated while simultaneously reconstructing thetomosynthesis image. A collimator can be provided for each of theplurality of x-ray sources and adjusted accordingly.

In another embodiment, a method of operating an imaging system includesfixing a number of x-ray sources in preselected positions, energizing aone of the x-ray sources including fluoroscopy imaging a body tissue,and then terminating use of the first x-ray source and energizing asecond x-ray source to continue imaging the body tissue. The x-raysources can be positioned in a common plane, and/or in a single vacuumchamber, or in a curved two dimensional array.

This brief description of embodiments of the invention is intended onlyto provide a brief overview of subject matter disclosed herein accordingto one or more illustrative embodiments, and does not serve as a guideto interpreting the claims or to define or limit the scope of theinvention, which is defined only by the appended claims. This briefdescription is provided to introduce an illustrative selection ofconcepts in a simplified form that are further described below in thedetailed description. This brief description is not intended to identifykey features or essential features of the claimed subject matter, nor isit intended to be used as an aid in determining the scope of the claimedsubject matter. The claimed subject matter is not limited toimplementations that solve any or all disadvantages noted in thebackground.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of embodiments of the inventioncan be understood, a detailed description of the invention may be had byreference to certain embodiments, some of which are illustrated in theaccompanying drawings. It is to be noted, however, that the drawingsillustrate only certain embodiments of this invention and are thereforenot to be considered limiting of its scope, for the scope of theinvention encompasses other equally effective embodiments. The drawingsare not necessarily to scale, emphasis generally being placed uponillustrating the features of certain embodiments of the invention. Inthe drawings, like numerals are used to indicate like parts throughoutthe various views. Thus, for further understanding of the invention,reference can be made to the following detailed description, read inconnection with the drawings in which:

FIG. 1 is a diagram that shows a perspective view of an exemplary mobileradiography unit with two displays according to one embodiment of thepresent disclosure.

FIG. 2 is a diagram that shows a perspective view of an exemplary mobileradiography unit of FIG. 1 positioned for travel.

FIG. 3 is a diagram that shows an exemplary embodiment of adisplay/monitor mounted to a boom assembly of a mobile radiography unitaccording to the present disclosure.

FIGS. 4A-4B are schematic diagrams that show a portable radiographyapparatus according to embodiments of the present disclosure.

FIG. 5 is a diagram that shows a perspective view of a mobileradiography unit that may provide fluoroscopic and tomosynthesis imagingaccording to embodiments of the present disclosure.

FIG. 6 is a diagram that shows x-ray source assemblies for exemplarymobile radiographic imaging systems including an x-ray source arrayembodiment that may include first and second radiographic x-ray sourcesand additional x-ray sources according to the present disclosure.

FIG. 7 is a diagram that shows alternate x-ray source assemblies forexemplary mobile radiographic imaging systems including an x-ray sourcearray embodiment that may include first and second radiographic x-raysources and additional x-ray sources according to the presentdisclosure.

FIG. 8A is a perspective view showing an arrangement of radiationsources for imaging according to an embodiment of the presentdisclosure.

FIG. 8B is a perspective view from above showing an arrangement ofradiation sources for imaging according to an embodiment of the presentdisclosure.

FIG. 8C is a perspective view from below showing the arrangement ofradiation sources shown in FIGS. 8A and 8B for imaging according to anembodiment of the present disclosure.

FIG. 8D is a perspective view showing an arrangement of radiationsources for imaging along with collimators for the source arrayaccording to an embodiment of the present disclosure.

FIG. 9A is a bottom view showing the array of x-ray sources.

FIG. 9B is a side view showing exemplary emitted beam patterns from thearray of x-ray sources of FIG. 9A.

FIG. 10 is a schematic view that shows the collimated beam intersectionpatterns at different distances from the source.

FIG. 11 is a logic flow diagram that shows a processing sequence forhybrid operation in tomosynthesis and fluoroscopy modes according toembodiments of the present disclosure.

FIG. 12A is a logic flow diagram that shows a processing sequence forusing depth imaging fluoroscopy according to embodiments of the presentdisclosure.

FIG. 12B is a schematic diagram that shows how an acquired image may beused in two different modalities according to embodiments of the presentdisclosure.

FIG. 12C is a schematic diagram that shows generation of a firsttomosynthesis image using a subset of x-ray source positions.

FIG. 12D is a schematic diagram that shows generation of a secondtomosynthesis image.

FIGS. 13A, 13B, and 13C are schematic diagrams that show use of animaging apparatus for tracking a progressive procedure at differentstages of a process.

FIG. 14 is a diagram that shows a radiography apparatus with an operatorinterface for setting up and monitoring an energization sequence for anarray of radiation sources.

FIG. 15 is a perspective view that shows a shield and different types ofradiation sources for combined tomosynthesis and general radiology.

FIG. 16 is a logic flow diagram that shows an exemplary method ofoperating exemplary mobile radiographic imaging systems for acquiringprojections images and generating the reconstruction ofthree-dimensional tomosynthesis images.

FIG. 17 shows simulations of exemplary projection images obtained usingx-rays from each x-ray source position.

FIG. 18 shows a tomosynthesis reconstruction image according to anembodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following is a detailed description of the preferred embodiments,reference being made to the drawings in which the same referencenumerals identify the same elements of structure in each of the severalfigures.

Where they are used herein, the terms “first”, “second”, and so on, donot necessarily denote any ordinal, sequential, or priority relation,but are simply used to more clearly distinguish one element or set ofelements from another, unless specified otherwise.

In the context of the present disclosure, the terms “viewer”, “viewingpractitioner”, and “observer”, are considered to be equivalent and referto the viewing practitioner or other person who views and manipulates anx-ray image on a display monitor or other viewing apparatus.

As used herein, the term “energizable” relates to a device or set ofcomponents that perform an indicated function upon receiving power and,optionally, upon receiving an enabling signal.

The term “actuable” has its conventional meaning, relating to a deviceor component that may be capable of effecting an action in response to astimulus, such as in response to an electrical signal, for example.

The term “modality” is a term of art that refers to types of imaging.Modalities for an imaging system may be conventional x-ray radiography,fluoroscopy or pulsed radiography, tomosynthesis, tomography,ultrasound, MMR, or other types of imaging. The term “subject” refers toa patient that is being imaged, or a portion thereof, and, in opticalterms, can be considered equivalent to the “object” of the correspondingimaging system. The patient may be human or animal, such as a mammal,and a region of interest may include a bodily region or a particularorgan or tissue of the human or animal.

The term “set”, as used herein, refers to a non-empty set, as theconcept of a collection of elements or members of a set is widelyunderstood in elementary mathematics. The term “subset”, unlessotherwise explicitly stated, is used herein to refer to a non-emptyproper subset, that is, to a subset of the larger set, having one ormore members. For a set S, a subset may comprise the complete set S. A“proper subset” of set S, however, is strictly contained in set S andexcludes at least one member of set S.

In the context of the present disclosure, the term “depth image” refersto a reconstructed image that represents depth information obtained fromprocessing multiple 2-D images or projection images of the subject,taken from different angles. Depth images may be obtained fromtomosynthesis, which does not typically provide full 3-D representation,or from computed tomography (CT) that provides more complete depthinformation and is considered to provide 3-D imaging. The noun“projection” may be used to mean “projection image”, referring to the2-D image that may be captured and used with other projection images toreconstruct a depth image. Reference is made to U.S. Pat. No. 8,172,633to Park et al., filed Apr. 4, 2007; U.S. Patent Application PublicationNo. 2011/0003109 by Slinker et al., filed Jul. 1, 2009; and U.S. Pat.No. 7,505,562 to Dinca et al., filed Apr. 19, 2007, all three of whichare incorporated by reference herein in their entirety.

FIG. 1 is a diagram that shows a perspective view of a mobileradiography unit that may use one or more portable radiographicdetectors or flat panel detectors adapted to acquire digital image dataaccording to radiation received from the x-ray sources according toembodiments of the present disclosure. The exemplary mobile x-ray orradiographic apparatus of FIG. 1 may be employed for digital radiography(DR), pulsed radiography or fluoroscopy, and/or tomosynthesis. As shownin FIG. 1, a mobile radiography apparatus 100 may include a moveabletransport frame 120 that includes a first display 110 and an optionalsecond display 110′ to display relevant information such as acquiredradiographic images and related data. As shown in FIG. 1, the seconddisplay 110′ may be pivotably mounted adjacent to the x-ray source 140to be viewable/touchable in a 360 degree range.

The displays 110, 110′ may be used to initiate or control (e.g., by wayof touch screens) functions such as generating, storing, transmitting,modifying, and printing of an obtained image(s) and may include anintegral or separate control panel (not shown) to assist in initiatingfunctions such as generating, storing, transmitting, modifying, andprinting of an obtained image(s). One or more of displays 110, 110′ maybe separable from the apparatus 100 frame. One or more of displays 110,110′ may act as display monitors for providing control messages andacknowledging instruction entry.

For mobility, the mobile radiographic apparatus 100 may have one or morewheels 115 and one or more handle grips 125 typically provided atwaist-level, shoulder-level, or at other levels that may be used by anoperator to guide the mobile radiographic apparatus 100 to its intendedlocation. A self-contained battery pack (e.g., rechargeable) may providesource power, which may reduce or eliminate the need for operation neara power outlet. Further, the self-contained battery pack may alsoprovide power to a motorized transport mechanism.

For storage, the mobile radiographic apparatus 100 may include anarea/holder for holding/storing one or more digital radiographic (DR)detectors or computed radiography cassettes. The area/holder may bestorage area 130 (e.g., disposed on the frame 120) configured toremovably retain at least one digital radiography (DR) detector. Thestorage area 130 may be configured to hold a plurality of detectors andmay also be configured to hold one size or multiple sizes of DRdetectors and/or batteries therefor.

Mounted to frame 120 is a support member 135, a column that supports oneor more x-ray sources 140, also called an x-ray tube, tube head, orgenerator that may be mounted to the support member 135. In theembodiment shown in FIG. 1, the supporting column (e.g., member 135) mayinclude a second section, a type of boom that extends outward afixed/variable distance from a first section where the second sectionmay be configured to ride vertically up and down the first section tothe desired height for obtaining the image. In addition, the supportcolumn may be rotatably attached to the moveable frame 120. In anotherembodiment, the tube head or x-ray source 140 may be rotatably coupledto the support member 135. In another exemplary embodiment, anarticulated member of the support column that bends at a joint mechanismmay allow movement of the x-ray source 140 over a range of vertical andhorizontal positions. Height settings for the x-ray source 140 may rangefrom low height for imaging feet and lower extremities to shoulderheight and above for imaging the upper body portions of patients invarious positions.

As shown in FIG. 2, for ease during transport of the mobile radiographicapparatus 100, the support member 135 and x-ray source 140 may bemanipulated into a more compact arrangement whereby components areplaced in closer proximity to frame 120. As shown in FIG. 2, the seconddisplay 110′ may be configured so that it may be placed in a viewableposition (e.g., operable) during transport of the mobile radiographicapparatus 100. When the mobile radiographic apparatus 100 is to be usedfor imaging, the support member 135 and x-ray source 140 may be extendedfrom the frame 120 for proper positioning (e.g., by the operator, auser, or x-ray technician) and the second display 110′ may be moved toanother viewable position such as shown in FIG. 1.

FIG. 3 is a diagram that shows an exemplary embodiment of adisplay/monitor used as a second display 110′ mounted to a boom assemblyof a mobile radiography unit according to the present disclosure. Asshown in FIG. 3, the second display 110′ may be mounted to a collimator345 of an x-ray source 340 of a support member 135 of a mobileradiography unit. In other embodiments, the collimator 345 may berotatably mounted to the x-ray source 340 so that the collimator 345(e.g., second display 110′) may swivel at least about 90 degrees, atleast about 180 degrees, or about 360 degrees. As shown in FIG. 3, thesecond display 110′ may include a plurality of handles 341 coupledthereto for ease of positioning. Alternatively, the second display 110′may be mounted (e.g., rotatably) to an x-ray source 340 above acollimator 345 of the boom assembly of the mobile radiography unit.

The Applicants have recognized the need for an imaging apparatus thatprovides improved tracking of interventional and other medicalprocedures, wherein the tracking operation of the imaging system adaptsto the needs of the practitioner and operates in both 2-D and depthimaging modalities. Moreover, the apparatus of the present disclosureshares acquired image data between imaging modalities, so that imagedata obtained for 2-D fluoroscopy may be reused for forming atomosynthesis image that has depth data. Embodiments of the presentdisclosure also allow for updating the tomosynthesis image with partialinformation that has been obtained from fluoroscopic imaging, thusproviding a wide range of imaging tools to the practitioner with reducedradiation dose to the patient. With improved visualization,interventional procedures may be performed in less time, furtherreducing radiation to patients and potentially using smallerconcentrations of contrast agent. In addition, because embodiments ofthe present disclosure may utilize an array of smaller x-ray sourcesarranged in a geometric pattern, one embodiment may allow the imagingsystem to be adapted to the type of imaging and radiation anglesnecessary for acquiring useful images, or adapting different sequencesof x-ray source energization to provide improved imaging from differentangles without requiring re-positioning of the x-ray sources.

In one embodiment, as shown in schematic form in FIG. 4A, a portable ormobile hybrid fluoroscopy apparatus 400 for obtaining images of apatient 414 has an array 410 of x-ray sources 426 in a fixed geometricarrangement, each x-ray source 426 configured to be individuallyenergized as part of a timed sequence of energizing a subset or all ofthe x-ray sources 426, and each x-ray source 426 in array 410 aimed toemit radiation toward a region of a subject, patient 414, to be imaged.In another embodiment, as shown in schematic form in FIG. 4B, a portableor mobile hybrid fluoroscopy apparatus 480 for obtaining images of apatient 414 has a source transport 411 for moving one or more x-raysources 426 along a curved path 412 in the directions indicate by arrow413 to position the one or more x-ray sources 426 at any of the samepositions as the fixed sources 426 in the x-ray source array 410 or atpositions in between those of the fixed x-ray source array 410. Thesingle x-ray source 426 may be configured to be fired multiple times atone position such as in a fluoroscopy mode, or as part of a timedsequential firing at each of several positions, such as in a tomographiccapture mode, as the x-ray source 426 is moved to firing positions alongthe curved path 412. The curved path 412 is configured to continuouslyaim the x-ray source 426 toward a region of the subject patient 414 asthe x-ray source 426 is moved. Thus, the description that follows isequally applicable to embodiments of the mobile hybrid fluoroscopyapparatuses 400 and 480.

An x-ray detector 420 may be separable from a support column 930 and maybe adapted to capture the digital x-ray images. X-ray sources 426 may bedisposed in a single plane, multiple planes, a two-dimensional curved orplanar array, or combination thereof in the embodiment of the mobilehybrid fluoroscopy apparatuses 400, and the source transport 411 of themobile hybrid fluoroscopy apparatuses 480 may be configured to move thesingle x-ray source 426 in a single plane, multiple planes, atwo-dimensional curved or planar array, or combination thereof. X-raysources 426 of the mobile hybrid fluoroscopy apparatuses 400 may bedisposed in a single vacuum chamber or may be configured so thatmultiple sources share a common vacuum chamber or so that each sourcehas its own vacuum chamber. X-ray detector 420 may be de-coupled fromarray 410 or transport 411, e.g., a free-standing detector, and bemanually repositionable so that a variable distance between array 410 ortransport 411 and detector 420 may be provided.

An image processor 430, such as a computer server or workstation,processes the acquired digital images and generates either 2-Dfluoroscopy or depth images as needed during a medical procedure. Aprocessing system having control logic processor 430 loads and executesa sequence of instructions, stored as a control program, for obtaining astored imaging pattern by energizing a subset or all of the x-raysources in a programmed sequence, wherein the programmed sequencecontrols which of the x-ray sources are included in the subset andcontrols timing for energizing each of the x-ray sources. According toan alternate embodiment of the present disclosure, processor 430 may bea dedicated Graphical Processing Unit (GPU). The GPU may be used as agraphic display processor with a fixed pipeline to a more capableprocessor for general purpose computing, matrix computing, imageprocessing, simulation and medical imaging using parallel processingover the programming pipeline. As one example, GPU architecture and itsparallel processing capabilities have been utilized for providinghardware-accelerated volume image rendering and other imaging, asdescribed in U.S. Patent Application No. 2006/0227131 entitled “FlatTexture Volume Rendering” by Schiwietz et al., which is incorporated byreference herein in its entirety.

A display 442 may be in signal communication with processor 430 and maybe adapted to display the acquired images. A mobile transport frame 920has column 930 that serves as a support structure for extending array410 or transport 411 toward patient 414 or other subject to be imaged.X-ray source array 410 or transport 411 may remain stationary duringimaging. Alternatively, x-ray source array 410 or transport 411 may bemoved during imaging, independent of the stationary detector 420. Thearray of x-ray sources 410 in FIG. 4A may have three or more x-raysources 426 and may be geometrically arcuate in a plane perpendicular tothe image plane in the embodiment that is shown, but may have any of anumber of alternate geometric configurations. Considered geometrically,the arc center of the source array 410 or the transport 411, shown as C1in FIGS. 4A and 4B may be generally located within the patient beingimaged, by placing the patient at the arc center, or within about onemeter of the patient. An arc 42 is represented as a dashed line in FIG.4A and the curved path 412 of FIG. 4B may be configured to be parallelthereto.

The source array 410 could alternately be designed so that fixed sources426 are peripherally arranged to be geometrically arcuate in a planeparallel to the image plane, or may have some other overall shape.Detector 420 may be positionable independent of source array 410 andtransport 411. According to an embodiment of the present disclosure, asshown in FIGS. 4A and 4B, transport frame 920 also houses processor 430for 2-D and depth image processing and presentation.

FIG. 5 is a diagram that shows a perspective view of a mobileradiography apparatus 900 that may provide both fluoroscopic or pulsedradiography and tomosynthesis imaging capability according toembodiments of the present disclosure. According to an embodiment of thepresent disclosure, a mobile radiography apparatus 900 may operate as atomosynthesis or fluoroscopy system, or a system adapted for othervolume imaging modes. As shown in FIG. 5, the mobile radiographyapparatus 900 may include a movable transport frame 920. Mounted to themoveable transport frame 920 may be a support column 930 that supportsan x-ray source array 940. As shown in FIG. 5, support column 930 mayinclude a second section 930 b that extends as a boom outward afixed/variable distance from a first section 930 a, where the secondsection 930 b may be configured to move (e.g., ride vertically) up anddown the first section 930 a to the desired height for obtaining theprojection images. The system also includes a digital x-ray detector 950that may be in signal communication with a system controller 915. Signalcommunication may be provided either wirelessly or in wired or tetheredform, so that detector 950 may be connected to system controller 915contained inside the moveable transport frame 920. Detector 950 may beseparately positionable, independent of x-ray source array 940components. The system controller 915 may implement and/or control thefunctions of the mobile radiographic/tomosynthesis system 900 (e.g.,functions provided through a console or control displays 110, 110′ inFIG. 1). The system controller 915 may include a general purposeprocessor, digital computer, microprocessor, RISC processor, signalprocessor, CPU, GPU, arithmetic logic unit (ALU), video digital signalprocessor (VDSP), dedicated processor, and/or similar computationalmachines, programmed for a range of positioning and imaging functionsaccording to the teachings of the present disclosure, as will beapparent to those skilled in the radiography imaging arts.

In certain exemplary embodiments, mobile radiography apparatus 900 mayprovide a tomosynthesis capability. A moveable mounted x-ray sourcearray 940 may, in addition, be supplied with a plurality of multipleindividually controlled x-ray sources 942, such as more than threesources 942, to provide a distributed x-ray source array with a variableexcitation pattern. FIG. 5 shows an embodiment of mobile radiographyapparatus 900 where multiple individually controlled x-ray sources 942in a linear arrangement or pattern provide distributed x-ray sources inan array. As shown in FIG. 5, x-ray source array 940 may alternativelyinclude a plurality of distributed x-ray power sources 942 where atleast one central source of the distributed x-ray power sources has full(e.g., standard) x-ray power. The central source, for example, may havea wide range of kVp settings, such as from about 50 kVp to about 150kVp, and high maximum mA output, such as from about 10 mA to about 400mA, in order to accommodate many different exam types for generalradiography.

The distributed sources that form the array may be disposed in aprescribed spatial relationship. The distributed sources may includelower power x-ray sources, which may also mean a narrow range of kVpsettings, such as from about 60 kVp to about 120 kVp for example, orsuch as from about 30 kVp to about 130 kVp, and a lower maximum mAoutput, such as from about 1 mA to about 100 mA. X-ray source array 940may use one or more collimators that adjust to form beams that aredirected towards the detector 950 and/or a patient P. The x-ray sourcearray 940 may also include positioning mechanisms, such as motors, thatallow for moving one or more sources or collimators and directing thebeam more accurately towards the detector 950 and/or patient P. Themoveable transport frame 920 may include first display 910, which may bepart of a control console to control at least the x-ray source array940. Further, the system controller 915 may coordinate operations of thex-ray source array 940, detector 950, and moveable transport frame 920(e.g., via operator actions using the first display 910). The systemcontroller 915 may control operations of the x-ray source array, whichmay include collimator settings, positioning devices and triggering ofimage acquisition by emission of x-rays from the sources. For example,the system controller 915 may control x-ray emission for tomosynthesis,or fluoroscopy imaging procedures and/or for general radiography imagingprocedures. The system controller 915 also may control operations ofdetector 950, which may include triggering of image acquisition processand transmission of the acquired images back to the controller. Inaddition, the system controller 915 may control the movement of thetransport frame 920.

Array of X-Ray Sources

The x-ray sources may be, for example, a distributed array offield-emission based x-ray sources, such as sources having carbonnanotube (CNT) cathodes, which may be peripherally arranged about acentral thermionic source. The x-ray sources may be stationary orrelatively fixed in position with respect to each other within thearray; the array itself may move as a single unit. This type of x-raysource may be capable of rapid on/off switching on the order ofmicroseconds. Other suitable x-ray sources may include paired pulsedconventional fluoro-capable thermionic sources that are spatiallyseparated. These options provide sufficient x-ray fluence with shortexposure times and simultaneously allow exposure sequences withoutoverheating. A carbon nanotube x-ray source may include one or morecathodes within a vacuum chamber, wherein each cathode may be formedfrom a large number of individual carbon nanotubes that are subject toexcitation energy and thereby emit electrons that are accelerated towardone or more anodes in the chamber.

The diagram of FIG. 6 shows an x-ray source array 1040 of a mobileradiographic imaging system that includes a first radiographic x-raysource 944 of thermionic type and collimator, and a second, third, andadditional x-ray sources 942 a, 942 b, 942 c, and so on, that may beindividually adjusted (e.g., collimated) and either permanently attachedor attached when needed (e.g., detachable). As shown in FIG. 6,according to an embodiment of the present disclosure, the firstradiographic x-ray source 944 may be a central one of the distributedsources. Alternatively, the first radiographic x-ray source may bethermionic, positioned at a center of the second array of peripherallydistributed sources. As shown in FIG. 6, the first radiographic x-raysource 944 may be a mobile/portable x-ray source/tube and may be adifferent type of x-ray source from the second distributed array oflower power carbon-nanotube x-ray sources. Other types of standardradiography and distributed array sources may be used. Detachablesources or the full detachable array 410 may be separately mounted fromthe support structure of fluoroscopy apparatus 400 (FIG. 4A) orsupported at one or more positions around the patient.

The diagram of FIG. 7 shows an alternate embodiment of an x-ray sourcearray 1140 of a mobile radiographic imaging system. The linear x-raysource array 1140 may include a directed first radiographic x-ray source944 and a directed second x-ray source array 948 comprising adistributed source attachment (e.g., linear) that may be eitherpermanently attached or attached when needed, e.g. as a detachablefixture 943 fixing sources 942 a-c. As shown in FIG. 7, the firstradiographic x-ray source may be positioned at a center of the array ofdistributed sources. In one embodiment, the first radiographic x-raysource may be a central member of the array 948 of distributed sources.In one embodiment, the plurality of distributed x-ray sources 942 may bemounted along a support 946. In one embodiment, the plurality ofdistributed x-ray sources 942 may have a prescribed spatial geometricrelationship, where the prescribed spatial geometric relationship may beone or more linear tracks, 2-D tracks, curves, polygons, rectangles or3D paths. In one embodiment, collimated distributed sources may be on acurved support to maintain a single distance from a corresponding pointon a detector. Exemplary distributed source attachment may have a firstposition for use and a second position for storage (e.g., folded asshown in FIG. 7) when not used.

FIGS. 8A, 8B, 8C, and 8D show various embodiments of source array 948with sources 942 in a generally elliptical or circular geometricarrangement with source 944 centered within the circle. According to anembodiment of the present disclosure, there may be about 64 sources 942in a circular arrangement of about 32 cm diameter; the diameter may bevaried as well as the curvature of the array or angular disposition ofthe sources within the array. An elliptical, polygonal, or randomizedsource arrangement may alternately be used to form a closed geometricloop of sources. A circle is one form of ellipse or, even moregenerally, a closed loop or closed curve structure. Triangles, squares,rectangles, pentagons, and hexagons are forms of polygons. Sources mayalso be distributed in a geometrically irregular arrangement.

In the FIG. 8A-8D arrangement, a collimator 960 may be provided forsource 944. Additional collimators 962 provide collimation forindividual sources 942. According to an embodiment of the presentdisclosure, each individual source 942 has its own collimator 962, as inthe embodiment shown in FIG. 8D, for example. Each collimator may beadjustable to accommodate the angle between the x-ray source anddetector. A number of subsequent figures intentionally omit showing thecollimator 962 in order to show other details more clearly.

FIG. 9A shows, from a bottom view, an exemplary configuration ofradiation sources 942 for radiography and tomosynthesis imaging similarto those shown in FIGS. 8A-8D. FIG. 9B shows a side view. The schematicview of FIG. 10 shows the intersection of collimated x-ray beams withplanes at different distances from the detector 950. In 1110, the beamintersects a plane at about 12 inches from the detector. In 1120, thebeam intersects a plane at about 6 inches from the detector. In 1130,the beam intersects a plane proximate to or at the detector.

The x-ray source array 948 may be part of a portable radiography system,as shown and described as mobile radiography apparatus 900 withreference to FIGS. 1, 2, 4, and 5, or may be installed in a fixedposition. With either a portable or fixed x-ray source configuration,the source array 948 may be used with a detector 950 that may beportable and not physically coupled to source array 948.

The logic flow diagram of FIG. 11 shows an exemplary programmed sequenceof operation for an imaging apparatus that uses x-ray source array 948,or one or more movable x-ray sources 949 for combined fluoroscopic andtomosynthesis imaging. The movable one or more sources 949 may beconfigured to be revolved about central axis A as indicated by the arrow951 to the same positions as each of the fixed sources in source array948, as shown in FIG. 11, and to positions between those of the fixedsources of source array 948. The programmed sequence thus allowssuccessive imaging for two or more modalities such as conventionalprojection radiography, fluoroscopy or pulsed radiography, andtomosynthesis, using the same fixed geometric arrangement 948 or themovable configuration 949. This advantageously provides the differenttypes of images within the same spatial configuration. According to thestored, programmed imaging sequence, an initial scanning step 200 mayobtain the projection 2-D images that are used for reconstruction of thedepth image in tomosynthesis processing. Scanning step 200 may usemultiple sources in array 948 and may use each of the x-ray sources inthe array 948, acquiring an image with the energization of each source.Scanning step 200 may also use the one or more movable sources 949,acquiring an image at each programmed position of the source 949 as itis revolved into positions about axis A. In a reconstruction and displaystep 210, image processor 430 uses the scanning step 200 results andgenerates, using a reconstruction algorithm, the depth image forpresentation on display 442. A fluoroscopy step 220 may be executed, inwhich one or more individual sources 942 in array 948, or the one ormore sources 949, are energized in order to generate 2-D fluoroscopicimages. Significantly, the array of sources 948 remain in their fixedpositions when the imaging modality is changed, such as when changingfrom tomosynthesis to fluoroscopy or from fluoroscopy to tomosynthesis.With regard to the movable one or more sources 949, it may remain in afixed position when the imaging modality is changed or it may begin orstop motion (revolving) when the imaging modality is changed, such aswhen changing from tomosynthesis to fluoroscopy or from fluoroscopy totomosynthesis. During step 220, an update step 230 executes, in whichthe depth image that was generated in reconstruction and display step210 may be at least partially updated according to the acquiredfluoroscopy image content that corresponds to some of the imageprojections originally obtained for the depth image. An optionalauto-reconfiguration step 240 may be executed based on detected movementof a catheter or other device or substance past a threshold position, orbased on operator movement or action, such as an explicit instruction,signal, button activation, or on detection of a change in the focus ofoperator attention, according to decision steps 250 or 260.Reconfiguration step 240 may change the excitation pattern of the x-raysource or sources used for the fluoroscopic imaging sequence and maycontinue the sequence, obtaining further fluoroscopic data.

In addition to adapting its fluoroscopic imaging behavior based onmotion information or practitioner prompting, the process of FIG. 11allows periodic update of the depth image that originates fromtomosynthesis reconstruction according to at least some portion of theimage content that may be subsequently obtained from fluoroscopicimaging. When the same x-ray source is used for tomosynthesis andfluoroscopy imaging, update of the tomosynthesis image may be performedbased on subsequent fluoroscopic content. As the angular aspect of thefluoroscopic image changes, another portion of the projection imagesthat were used to reconstruct the depth image may be updated; thus, thecorresponding tomosynthesis projection may be refreshed accordingly.Thus, change in image capture angle may cause a corresponding change inthe image data content used for reconstructing the tomosynthesis image.

The logic flow diagram of FIG. 12A shows an alternate sequence ofoperation for providing a hybrid fluoroscopic depth imaging thatdynamically adjusts operation based on how quickly the system is able torespond to detected motion of the subject. Where detected motion isrelatively slow during a procedure, fluoroscopic image capture may notbe used to refresh a 2-D display, but rather used to provide an updateddepth imaging display. Where motion or movement speed is above apredetermined threshold, the depth image may either not be updated, ormay be updated periodically, but the 2-D fluoroscopy display may becontinuously updated. Scanning step 200 and reconstruction and displaystep 210 form the depth image from tomosynthesis imaging. Eachprojection image obtained in the tomosynthesis scan has correspondingangular sequence information, allowing frame-by-frame update of tomosynthesis projections with fluoroscopic content as fluoroscopy proceeds.A fluoroscopy step 222 then executes a fluoroscopy or pulsed radiographyimaging sequence, obtaining a succession of 2-D fluoroscopic images fordisplay. A decision step 252 checks for movement of the subject contentto determine whether to continue with conventional 2-D fluoroscopy in afluoroscopy step 224 or to update the depth image from tomosynthesisusing the fluoroscopic image data that was obtained. Where movement isslow, a mapping step 242 maps fluoroscopy imaging results to the depthimage projections to provide information for an update step 244. Updatestep 244 provides the newly obtained fluoroscopy image data toreconstruction and display step 210 so that the depth image can bereconstructed.

In one method of operation, a fluoroscopy sequence may be performedutilizing some or all of the sources 948 in a pulsed sequence, anddisplayed on display 442. Such an imaging sequence may not significantlyaffect observable phenomena displayed on display 442 as viewed by anoperator of the imaging system as compared with the conventionalfluoroscopy mode of using only one pulsed source. The set of fluoroscopyimages obtained this way may be captured and stored in order to be usedto generate a depth image using tomographic reconstruction methods asdescribed herein.

For the sequence of FIG. 12A, movement may be detected by image analysisof the fluoroscopic image data stream, using methods well known in theimaging arts for detecting subject movement from successive images. Bytracking movement in this sequence, the system adapts to providedifferent types of image display for the practitioner, with the addedbenefit of depth display when there is sufficient time for update of thereconstructed image. According to an embodiment of the presentdisclosure, viewer override is also provided, so that movement detectiondoes not determine how imaging results are provided; instead, thepractitioner decides to maintain either depth imaging or fluoroscopyimaging during parts of a procedure.

FIG. 12B shows how acquired projection images 952 may be used in twodifferent modalities according to an embodiment of the presentdisclosure. Although FIG. 12B illustrates a fixed source arrayconfiguration 948, as described above with reference to FIGS. 11 and12A, an embodiment using the one more movable source(s) 949, asdescribed above with reference to FIGS. 11 and 12A, may be used and isequally applicable. Thus, the following description referring tosequential firing of fixed sources in source array 948 may also beimplemented using the one or more movable source(s) 949 being moved(revolved) into equivalent positions for firing. For tomosynthesis, asshown in the top portion of FIG. 12B, x-ray source array 948, or movablesource 949, may be used to form a set 470 of images, with one image 952corresponding to each source 942 of array 948, or each position ofsource 949. Using this energization pattern for fixed sources 942, atomosynthesis image may be generated without requiring movement of thex-ray sources of array 948 and detector relative to the imaged subject.Using movable one or more sources 949, a tomosynthesis image may begenerated with minimal number of sources. Depth image reconstructiontechniques then generate the depth image using set 470 of 2-D images.For fluoroscopy, as shown in the bottom portion of FIG. 12B, a single2-D image may be repeatedly acquired, as represented by an image 952that corresponds to image 952 f in set 470. Using this mapping, it canreadily be seen how later acquisition of a fluoroscopy image may serveto help update the depth image content obtained earlier. Significantly,the source-detector spatial relationship may be the same when image 952f is initially obtained as part of tomosynthesis set 470 and when theimage from source 942 f is later obtained for fluoroscopy.

According to an embodiment of the present disclosure, images 952 thatare repeatedly obtained for fluoroscopy, using the same x-ray source942, may be compared against earlier images obtained and used fortomosynthesis to determine whether or not the reconstructed depth imagecontent is still accurate or needs to be updated. When image analysisshows, for example, that the tomosynthesis depth image that was obtainedearlier might be misleading, a precautionary message may be displayedwith the tomosynthesis depth image, indicating significant changes inimage content. In this way, the results of fluoroscopy imaging may serveas a check on the overall accuracy of tomosynthesis reconstruction anddepth information that is provided. For example, a tomosynthesis imagetaken earlier may show a catheter at a particular position. As cathetermotion progresses, the tomosynthesis image becomes less accurate, andmay even be misleading. Comparison of fluoroscopic images obtained fromone of the same x-ray source positions that were used for thetomosynthesis reconstruction may help to indicate when the tomosynthesisinformation is no longer accurate, so that either a new reconstructionis needed or some precautionary message posted when the depth imagedisplays. Any of a number of image processing methods that detect changein a feature or movement of position of a feature may be applied inorder to check on whether or not depth image update is needed.

The number of most recently captured images for tomosynthesis imagingmay be a one-time selectable number that remains constant during theoperation of the imaging system. Display 442 (FIGS. 4A-4B) may be usedto show the fluoroscopy image alongside the tomosynthesis image or toswitch display modes between fluoroscopy and tomosynthesis.

Sequencing of X-Ray Sources

When used for tomosynthesis imaging, different proper subsets of x-raysource array 948, or different positions of one or more movable sources949 may be used for successive tomosynthesis reconstructions, as shownin the example of FIGS. 12C and 12D. In FIG. 12C, a first subset ofx-ray sources {942 a, 942 b, 942 c, 942 d, 942 e, and 942 f} or movablex-ray source 949 in equivalent positions, may be used to generate acorresponding first subset of images {952 a, 952 b, 952 c, 952 d, 952 e,and 952 f} that may then be used to reconstruct and display a firsttomosynthesis image. Similarly, a second subset of x-ray sources {942 b,942 c, 942 d, 942 e, 942 f, and 942 g} may be used to generate acorresponding second subset of images {952 b, 952 c, 952 d, 952 e, 952f, and 952 g} to reconstruct and display a second tomosynthesis imagehaving slightly different depth content.

Alternatively, when using source array 948 with sources 942 that arecapable of rapid switching, or one or more movable sources 949, a numberof source excitation or firing sequencing arrangements may be used forfluoroscopic imaging, including sequencing in a pattern thatautomatically adjusts according to movement tracking, such as fortracking a catheter or a contrast agent traveling through a vein orartery or progressing through some other body cavity, for example.Referring to FIGS. 13A, 13B, and 13C, source array 948, or one or moremovable sources 949, is configured for a circular or ellipticaloperation. At a time t1 in FIG. 13A, with a catheter as far as positionA, a source at position 942 a may be energized and detector 950 acquiresimage data for an imaging region with corresponding position A′ shown ondisplay 442. At a different time t2 in FIG. 13B, such as immediatelyfollowing time t1, a source at position 942 b may be energized anddetector 950 acquires image data with the catheter extended to animaging region at position B. The corresponding image shows catheterextension to position B′. At a later time t3 in FIG. 13C, such asimmediately following time t2, a source at position 942 c may beenergized and detector 950 acquires image data with the catheterextended to an imaging region near position C. The corresponding imageshows catheter extension to position C′. The rate at which the differentx-ray source positions 942 are achieved, sequentially from one to thenext, may be predetermined based on the type of procedure or may bebased on tracking the progress of a particular procedure, so thatdetection of progress or of particular events may be used to control thepattern or position of the x-ray source or sources at a firing time t.

According to an alternate embodiment of the present disclosure, morethan one x-ray source may be used for obtaining fluoroscopy images, withonly one x-ray source energized at a time. Thus, for example, twoadjacent or separated x-ray sources 942 in array 948 of FIGS. 9A-9C arealternately energized in a repeated cycle, thus reducing the heat loadon any single source. Three or more x-ray sources could alternately beenergized in this way for obtaining fluoroscopic image content.

FIG. 14 shows an embodiment of a radiography apparatus 1000 that hassource array 948 with sources 942 in an arrangement that may beessentially circular. An operator interface 460 provides a graphic 448that represents the x-ray source arrangement and that may show whichsource 942 may be energized or scheduled to be energized as part of astored pattern 452 that stores an exposure sequence for execution byapparatus 1000. The stored pattern may be used for tomosynthesis imagingor for fluoroscopic imaging, during which an individual source 942 ortwo or more sources 942 may be repeatedly energized to providefluoroscopic imaging along a predetermined path.

According to an embodiment of the present invention, an imaging sequenceuses the central thermionic x-ray source 944 (FIG. 9A) for pulsed imageor fluoroscopic imaging due to its heat dissipation characteristics andcollimation ability, allowing suitable dose control. Peripherallydistributed CNT or other distributed sources are then energized uponcommand as needed in order to generate images that help clarify thepositional relationship of an interventional device such as a catheterto patient anatomy. This can be useful, for example, at a catheter tiplocation where branches or overlapping vessels or other features mightotherwise obstruct the view if obtained using the central source 944.The ability to quickly acquire a projection image from an alternateangle, without physical repositioning of the source, can help to showfeatures that would otherwise be obstructed or momentarily unclear. Thethermionic source 944 may then be re-energized as the procedurecontinues. Switching between different sources may also be used to helpbalance the heat load within source array 948. One or more heat sensors970 may be monitored and monitoring results used to adjust the patternof source energization to control heat buildup in array 948.

According to an embodiment of the present invention, operator interface460 of FIG. 14 allows user programming for setting up one or moreexposure sequences as stored patterns 452. For this purpose, aninstruction entry area 450 may be provided on display 442, allowing theuser to schedule how long and in what order each source 942 is energizedfor a particular exposure sequence. Each x-ray source may be aimed at animaging region of the subject to be imaged. According to an embodimentof the present disclosure, the stored schedule provides instructions forenergizing each member of a subset of sources 942 in sequential orderand for a programmed time interval. The subset may include each source942 or may exclude one or more of the sources in the array 948. Thus,for example, a particular exposure sequence may be configured and storedfor tracking a contrast agent that is expected to progress through avein or other body cavity at a predictable rate.

In an alternative embodiment, the sequence order may be programmed andstored, but timing may not be stored; instead, the practitioner may begiven the option to index through the programmed sequence during aprocedure by using a switch 462 such as a foot pedal or by providing anaudible signal or other prompt that instructs apparatus 1000 to advanceto the next programmed step in sequence. In this way, the operatorindexes through a predetermined sequence of steps that energizedifferent x-ray sources at each step.

According to an alternate embodiment of the present disclosure, switch462 may be an array of activation buttons, with each button configuredto energize a single x-ray source 942. Display 442 may alternately be atouch screen for providing an activation-button interface to acceptviewer instructions. In this way, exposure using multiple sources may becontrolled by the practitioner so that the images obtained, whether fortomosynthesis or fluoroscopy, are at an optimal angle or set of anglesand with a preferred exposure type for diagnostic assessment. It can beappreciated that a default timeout may also be used, so that operatorinstructions advance the sequence or extend the exposure time fromspecific sources in the array 948.

In one embodiment, the arranged or distributed low power source(s) maybe an array 948 of carbon-nanotube x-ray sources that are disposed in asingle vacuum chamber and are attached to a common fixture (FIGS.8A-8D). In one embodiment, a plurality or all of the carbon nanotubecathodes of the x-ray sources 942 may be arranged in a circularformation such that their electron beams 852 are emitted in an outwarddirection in relation to a center of the circular arrangement. Theemitted electron beams 852 may each be directed at one of acorresponding plurality of anodes all sharing a common electrical anodepotential. Another anode embodiment may include a disc 850 with orwithout a central opening therethrough. For example, this disc anodeembodiment may have a continuous, inward facing, annular beveled edge851 (FIG. 8C) formed at a constant angle relative to an axis through thecenter of the circular arrangement (central axis), so that the electronbeams 852 from the plurality of cathodes may impinge the beveled edge851 of the anode disc 850 to generate x-ray emission at a suitable angletoward digital radiographic detector 950 (FIG. 9B). The disc anode 850may rotate about the central axis so the focal points on the bevelededge 851 impacted by the electron beams 852 are distributed over thelarger surface area, as compared to a stationary anode, to reduce damage(e.g., overheating, melting). In a similar fashion, the carbon nanotubecathodes may be disposed in a circular arrangement to emit an electronbeam inward toward the central axis while the disc anode is formed suchthat its beveled edge faces outward, away from the central axis, at anangle suitable to direct x-rays toward the detector as explained herein.

As shown in FIG. 15, the x-ray hardware may include embodiments that usea central x-ray source 944 with a more traditional collimator 960. Thiscentral x-ray source may be used to capture traditional 2-D x-rayimages.

Although a circular arrangement of distributed low power x-ray sourcesare shown here, other linear or non-linear arrangements or evenprescribed geometric patterns (e.g., shapes, stars, diamonds, regular orirregular combinations, repeating) may be used with correspondingselectable array of collimation windows that may provide combinedtomosynthesis and projection x-ray imaging.

Two different type of x-ray sources (i) general radiation source and(ii) distributed array of certain number of sources (e.g., lower power)may be included in a single x-ray source for a radiographic imagingsystem according to embodiments of the present disclosure.

One exemplary embodiment for the distributed array of sources may be aconfiguration that may include 30 or more distributed sources in a unit(e.g., unit array of distributed sources) at sides (e.g., each of 3-10sides around a central area) to make an arrangement, which configurationmay be separated and individually attached by unit array (or fastenedtogether in a single entity) to a mechanical housing (e.g., tube head)of the imaging system. For certain exemplary embodiments, the unitarrays are not co-planar and may implement a different source-to-imagedistance (SID) for an imaging event or examination. For example, theunit arrays may be selectively co-planar, for example, two sides atdifferent depths, three of four sides at different planes. Further, the(vertical, horizontal) distance between the unit arrays may be the sameor different (e.g., increasing). Alternatively, adjacent or oppositepairs of unit arrays may have equal SIDs or be co-planar. Such avariation in arrangement may allow for a fixed x-ray source arrangementto implement a greater range of subject distances.

Various arrangements of source array 948 are possible, includingexemplary embodiments that provide source array 948 in movable sections,with each section having one or more x-ray sources 942 for example. Thiswould allow repositioning of x-ray sources 942 to provide a certainamount of overlap to radiation beam paths or to alter the effectivesource-to-image distance (SID). For example, a chest x-ray examinationmay use a longer SID than a head x-ray examination and accordingly,movement (e.g., spatial re-positioning and/or rotation) of the unitarrays may allow multiple distances or SIDs to be implemented with asingle aperture (e.g., fixed collimation, pinhole) for each distributedsource. Collimation may be adjusted to compensate for beam changes withangle.

In one embodiment, additional collimation may be used with a collimatordisposed at a distance closer (e.g., 6 inches-2 feet) to the detector toprovide an outer limitation to the collimated beams of the distributedarray of sources.

In one embodiment, the unit arrays may be attached, adjusted and/orremoved without tools. In one embodiment, the unit arrays may beattached and/or rotated between two positions where a first position maybe outside an area traversed by a central x-ray beam (e.g., generalradiology beam) and a second position to cross or cover the areatraversed by the central x-ray beam. The second position in such aconfiguration can reduce an angular disbursement of beams from thedistributed array of sources.

In one embodiment, a plurality of unit arrays (e.g., 6-8 unit arrays)may be implemented to move between a small retracted configuration andunfold multiple times to form a prescribed linear or non-linearconfiguration (e.g., multiple straight lines of sources or unit arrays),which can extend in multiple directions from/around a central beam.

In one embodiment, a plurality of unit arrays (e.g., 6-8 unit arrays)may be implemented as individual straight lines sources, but configuredto approximate a circle.

Exemplary system and/or method embodiments according to the presentdisclosure may be used for in-room radiographic imaging systems and/orportable tomosynthesis. Portable tomosynthesis imaging may be able toprovide the sought information at the bedside without subjecting thepatient to the risks of transport to radiology. For example,tomosynthesis imaging can supply the required information to diagnosepatient conditions that are non-differentiable with standard projectionx-ray imaging such as chest x-rays.

According to an embodiment of the present invention, fluoroscopy may beeffected using two or more adjacent x-ray sources, sharing the heat loadthat may be generated by repeated energization. Various alternatingpatterns are used, including using a subset of two or three x-raysources that are adjacently disposed in the source array and notemploying a sequence that energizes each x-ray source in the subset anequal number of times and wherein no x-ray source may be energized twicein sequence.

Digital Radiography (DR) Detector

The x-ray detector may be a digital x-ray detector with signal to noiseratio performance at low exposure to allow readout of the exposuresequences. According to an embodiment of the present disclosure, a DRdetector for fluoroscopic imaging has a very high frame rate. Forexample, the x-ray detector may have a frame rate of about 30-60 framesper second; however, lower rates can still be usable. The DR detectorshould have excellent signal to noise ratio performance at low exposureto allow rapid readout of the rapid exposure sequences. According to anembodiment of the present disclosure, the digital detector employssensors of complementary metal-oxide semiconductor (CMOS) technology.

The DR detector may be independent from the x-ray source array,mechanically de-coupled from the x-ray sources so that it can bepositioned separately. The DR detector may be not movable from its fixedposition during tomosynthesis or fluoroscopic imaging. This arrangementallows stereo images to be obtained from any of a number of differentview angles, and allows the angular relationship of images to bedictated by the source array arrangement and source-to-image distance(SID), rather than being fixed, such as may be required with C-armarrangements. The x-ray sources may be moved during a procedure to allowimproved visibility.

Image Processor

The image processing logic must be capable of rapid spatial frequencyprocessing. Lag time between image acquisition, processing, and datatransmission must be reduced to low levels, so that response and refreshtime of the DR detector and associated components may be as low aspossible.

The flow chart of FIG. 16 shows an exemplary method for acquiringprojection images and reconstruction of three-dimensional tomosynthesisimages, according to an embodiment of the present disclosure. The methoddescribed may use embodiments of mobile radiography apparatus shown inFIG. 5, for example. Methods for image capture, processing, andpresentation given in the present disclosure may be applied to othermobile or stationary imaging apparatus, without limitation to aparticular type of system.

As shown in FIG. 16, in a positioning step 1210, the detector and x-raysource array may be positioned. For example, the x-ray source may bemoved to its initial position and the detector may be positioned suchthat the patient P may be interposed between the detector and x-raysource.

For an embodiment of exemplary mobile radiographic/tomosynthesis unit900 of FIG. 5, the initial x-ray source array position may be set by thelocation of transport frame 920 and the support column 930 to which thesource array may be coupled. The height, extent and rotation positioningof first section 930 a and second section 930 b of support column 930,or positioning elements that are themselves connected to support column930, may be used to position the x-ray source array 940 to the initialdesired location with respect to the patient.

Following positioning step 1210 in FIG. 16, an image acquisition step1220 optionally acquires one or more scout images, then acquires aseries of projection images at different x-ray source positions. Each ofthe projection images may be acquired while corresponding individualx-ray sources are triggered. In one embodiment, the first radiographicx-ray source may operate as a central one of the distributed sources. Ina transfer step 1230, the acquired projection image data may be received(e.g., transferred back from the detector to the system) by control andprocessing components of the system controller. The projection imagesmay be displayed on display 910 and/or undergo a quality check (e.g.,automated or by the operator) before being further processed. Theprojection image data may also be processed in transfer step 1230 topermit raw, partially-processed or fully-processed images ortomosynthesis slices to be stored (e.g., to support temporality at thedetector) and/or sent to remote locations.

Continuing with the FIG. 16, sequence, tomosynthesis imagereconstruction may be performed (e.g., real-time) using the acquiredcorrected projection image data in a reconstruction step 1240. Imagereconstruction may use processes similar to those used for conventionaltomosynthesis imaging. For example, as will be appreciated by thoseskilled in the art, back projection, filtered back projection, iterativereconstruction, or other known reconstruction techniques may be used. Inone exemplary embodiment, a particular position of the source withrespect to the detector may be determined by knowledge of the positionof the x-ray source array and the detector based upon the values set byan operator, or automatically determined according to image capturetiming or by using a grid alignment system to adjust the values or by atethered connection to source and detector positioning circuitry, forexample. The reconstructed volume may be provided on display 910 in adisplay step 1250.

The reconstructed volume may alternately undergo a quality check beforedisplay. In one embodiment, the reconstruction volume may be storedafter the quality check (e.g., before display). Further, the display maybe used to view underlying projection images or projection imagesgenerated by the system, or to view the tomosynthesis reconstructionsthemselves. Further, underlying data and/or reconstructed tomosynthesisimages may be transmitted to a remote system for additional analysis ordisplay.

FIG. 17 shows simulations of exemplary projection images 1262 fortomosynthesis obtained using x-rays from each source position of acircular source array 948. In practice, a smaller number of images thanthose shown may be all that is needed for tomosynthesis reconstruction.

FIG. 18 shows a tomosynthesis reconstruction image 1300 according to anembodiment of the present disclosure. The tomosynthesis image 1300displays to the practitioner as a 2-D slice extracted from the volumedata.

One embodiment utilizes a computer program with stored instructions thatperform on image data that may be accessed from an electronic memory. Ascan be appreciated by those skilled in the image processing arts, acomputer program of an embodiment of the present invention may beutilized by a suitable, general-purpose computer system, such as apersonal computer or workstation that acts as an image processor.However, many other types of computer systems may be used to executecomputer programs of the present invention, including an arrangement ofnetworked processors, for example. The computer program for performingmethods of the present invention may be stored in a computer readablestorage medium. This medium may comprise, for example; magnetic storagemedia such as a magnetic disk such as a hard drive or removable deviceor magnetic tape; optical storage media such as an optical disc, opticaltape, or machine readable optical encoding; solid state electronicstorage devices such as random access memory (RAM), or read only memory(ROM); or any other physical device or medium employed to store acomputer program. The computer program for performing methods of thepresent invention may also be stored on computer readable storage mediumthat may be connected to the image processor by way of the internet orother network or communication medium. Those skilled in the art willfurther readily recognize that the equivalent of such a computer programproduct may also be constructed in hardware.

It is noted that the term “memory”, equivalent to “computer-accessiblememory” in the context of the present disclosure, may refer to any typeof temporary or more enduring data storage workspace used for storingand operating upon image data and accessible to a computer system,including a database. The memory could be non-volatile, using, forexample, a long-term storage medium such as magnetic or optical storage.Alternately, the memory could be of a more volatile nature, using anelectronic circuit, such as random-access memory (RAM) that may be usedas a temporary buffer or workspace by a microprocessor or other controllogic processor device. Display data, for example, may be typicallystored in a temporary storage buffer that may be directly associatedwith a display device and may be periodically refreshed as needed inorder to provide displayed data. This temporary storage buffer may alsobe considered to be a memory, as the term is used in the presentdisclosure. Memory may be also used as the data workspace for executingand storing intermediate and final results of calculations and otherprocessing. Computer-accessible memory may be volatile, non-volatile, ora hybrid combination of volatile and non-volatile types.

It is understood that computer program products of the present inventionmay make use of various image manipulation algorithms and processes thatare well known. It will be further understood that the computer programproduct embodiments of the present invention may embody algorithms andprocesses not specifically shown or described herein that are useful forimplementation. Such algorithms and processes may include conventionalutilities that are within the ordinary skill of the image processingarts. Additional aspects of such algorithms and systems, and hardwareand/or software for producing and otherwise processing the images orco-operating with the computer program products of the presentinvention, are not specifically shown or described herein and may beselected from such algorithms, systems, hardware, components andelements known in the art.

The invention has been described in detail, and may have been describedwith particular reference to a suitable or presently preferredembodiment, but it will be understood that variations and modificationsmay be effected within the spirit and scope of the invention. Thepresently disclosed embodiments are therefore considered in all respectsto be illustrative and not restrictive. The scope of the invention isindicated by the appended claims, and all changes that come within themeaning and range of equivalents thereof are intended to be embracedtherein.

What is claimed is:
 1. An imaging system comprising: an x-ray assemblyaimed at an imaging region of a patient, the x-ray assembly configuredto be energizable to emit ionizing radiation from one or multipledifferent spatial positions toward the imaging region; control hardwareconfigured to energize the x-ray assembly to emit ionizing radiation atpredetermined times from each of the one or more of the spatialpositions; and a digital x-ray detector in digital communication withthe imaging system, the digital x-ray detector to capture a radiographicimage of the imaging region of the patient in response to energizing thex-ray assembly, wherein a first mode of operation of the imaging systemcomprises energizing the x-ray assembly to emit ionizing radiation froma first spatial position toward the imaging region of the patient, asecond mode of operation of the imaging system comprises energizing thex-ray assembly to emit ionizing radiation multiple times each from adifferent one of the spatial positions, and wherein the control hardwareis configured to switch the imaging system between the first and secondmodes of operation in response to an event occurring in the imagingregion of the patient as captured in a radiographic image.
 2. The systemof claim 1, wherein the detector is configured to capture and store aplurality of radiographic images of the imaging region of the patient inresponse to operating the imaging system in the second mode ofoperation, and wherein the captured plurality of images are used toreconstruct a tomographic image of the imaging region of the patient. 3.The system of claim 2, wherein one or more stored radiographic images ofthe imaging region of the patient captured in response to operating theimaging system in the first mode of operation are used together with theplurality of images captured in the second mode to reconstruct atomographic image of the imaging region of the patient.
 4. The system ofclaim 1, wherein the control hardware comprises non-transitory storedcontrol program instructions operable to controllably energize the x-rayassembly in a programmed firing sequence, and wherein the firingsequence defines the predetermined times and the one or more of thespatial positions.
 5. The system of claim 4, wherein the controlhardware further comprises: non-transitory stored control programinstructions operable to controllably energize the x-ray assembly in aplurality of programmed firing sequences; and input means for receivingan input from an operator of the imaging system to activate a selectedone of the plurality of programmed firing sequences.
 6. The system ofclaim 1, wherein the control hardware comprises an input means forreceiving an input from an operator of the imaging system to switch theimaging system between the first and second modes of operation.
 7. Thesystem of claim 1, wherein the control hardware comprises an input meansfor receiving an input from an operator of the imaging system to selectthe predetermined times and the one or more of the spatial positions. 8.The system of claim 1, wherein a third mode of operation comprisesenergizing the x-ray assembly one or more times from the first spatialposition toward the imaging region of the patient, energizing the x-rayassembly one or more times from a second spatial position toward theimaging region of the patient, alternating between energizing the x-rayassembly one or more times from the first spatial position and from thesecond spatial position toward the imaging region of the patient, or acombination thereof.
 9. The system of claim 1, wherein the x-rayassembly comprises a plurality of x-ray sources in a fixed spatialarrangement in relation to one another, and wherein each of theplurality of fixed x-ray sources correspond to one of the differentspatial positions.
 10. The system of claim 9, further comprising afixture to secure the plurality of x-ray sources all in a fixed firstposition in relation to the imaging region of the patient, wherein thefixture is repositionable to secure the plurality of x-ray sources allin a fixed second position in relation to the imaging region of thepatient.
 11. The system of claim 9, wherein the x-ray sources comprise aplurality of cathodes arranged along an arc to each emit an electronbeam radially outward from a center of the arc toward a commonsubstantially circular anode, the anode comprising a rotating dischaving a continuous anode surface receiving the electron beams andemitting x-rays in response thereto.
 12. The system of claim 1, whereinthe x-ray assembly comprises a movable x-ray source, the movable x-raysource configured to be movable to each of the different spatialpositions.
 13. The system of claim 12, wherein the x-ray assemblycomprises two or more movable x-ray sources, the movable x-ray sourcesconfigured such that at least one is movable to the different spatialpositions.
 14. The system of claim 1, wherein the control hardwarecomprises non-transitory stored control program instructions operable toswitch the imaging system between the first and second modes in responseto the imaging system detecting the event occurring in the imagingregion of the patient.
 15. The system of claim 14, wherein the eventoccurring in the imaging region of the patient is automaticallydetectable by the imaging system in the radiographic image of theimaging region.
 16. The system of claim 15, wherein the event occurringin the imaging region of the patient is automatically detected by theimaging system operating in the first mode.
 17. The system of claim 16,wherein the control program switches an operating mode of the imagingsystem from the first mode to the second mode automatically in responseto the imaging system automatically detecting the event occurring in theimaging region of the patient.
 18. The system of claim 17, wherein theevent occurring in the imaging region of the patient occurs in a bodycavity or fluid vessel of the patient.
 19. The system of claim 18,wherein the event occurring in the imaging region of the patientcomprises a radio opaque object or a radiographically detectible fluidmoving through the body cavity or fluid vessel of the patient.
 20. Thesystem of claim 1, wherein the event occurring in the imaging region ofthe patient comprises a radio opaque object or a radiographicallydetectible fluid moving through a body cavity or fluid vessel of thepatient.
 21. An imaging system comprising: an x-ray assembly aimed at animaging region of a patient, the x-ray assembly configured to beenergizable to emit ionizing radiation from one or multiple differentspatial positions toward the imaging region; control hardware configuredto energize the x-ray assembly to emit ionizing radiation atpredetermined times from each of the one or multiple different spatialpositions; and wherein a first mode of operation of the imaging systemcomprises energizing the x-ray assembly to emit ionizing radiation froma first spatial position toward the imaging region of the patient, asecond mode of operation of the imaging system comprises energizing thex-ray assembly to emit ionizing radiation multiple times each from adifferent one of the spatial positions, and wherein the control hardwareis configured to automatically select the predetermined times andmultiple spatial positions to energize the x-ray assembly in response toan event occurring in the imaging region of the patient as captured in aradiographic image.